Chemical Risk Assessment for Australian Workplaces

A chemical risk assessment is a systematic evaluation of the health and safety risks associated with the use, storage, handling, generation, or disposal of hazardous chemicals in a workplace. It identifies the specific chemicals present, the hazard properties of each chemical (toxicity, flammability, reactivity, corrosivity), the routes and levels of exposure that workers and others may experience, and the controls required to eliminate or minimise those exposure risks.

Chemical hazards are among the most complex to assess accurately because the risk depends not only on the inherent hazard properties of the chemical — its toxicity, carcinogenicity, flammability, or reactivity — but also on the exposure conditions: the concentration and duration of exposure, the route of entry (inhalation, skin contact, ingestion, injection), and the susceptibility of the exposed individual. A chemical that is acutely toxic at high concentrations may be safe at low concentrations; a chemical that is safe for occasional short-duration exposure may cause serious health effects with daily long-term exposure below the acute toxicity threshold.

In Australian workplaces, chemical risk assessment is required under the WHS Regulation 2025 for any workplace that uses, handles, generates, stores, or disposes of hazardous chemicals. The Hazardous Chemicals Code of Practice issued by Safe Work Australia provides detailed guidance on the assessment and control of chemical risks, including the use of Safety Data Sheets (SDS), the comparison of exposure against Workplace Exposure Standards (WES), and the selection of exposure controls in accordance with the hierarchy of controls.

The legal framework governing chemical risk in Australian workplaces is multi-layered, reflecting the intersection of WHS law, chemical classification and labelling requirements, and occupational exposure limits.

**WHS Regulation 2025:** Chapter 7 of the WHS Regulation imposes specific duties on PCBUs in relation to hazardous chemicals. PCBUs must obtain a current SDS from the manufacturer or supplier for each hazardous chemical used at the workplace, make the SDS available to workers, and use the information in the SDS to inform the risk assessment and control selection. The Regulation also specifies requirements for the storage of dangerous goods, the management of chemical incompatibilities, and the disposal of chemical waste.

**Globally Harmonised System (GHS):** Australia has adopted the United Nations Globally Harmonised System of Classification and Labelling of Chemicals, which is implemented through the WHS Regulation. GHS classifies chemicals into hazard categories (acute toxicity, skin corrosion, serious eye damage, carcinogenicity, reproductive toxicity, specific target organ toxicity, flammability, and others) and specifies standardised label elements and SDS format. Understanding GHS hazard statements and precautionary statements is essential for interpreting SDS information in a chemical risk assessment.

**Workplace Exposure Standards (WES):** Safe Work Australia publishes the Workplace Exposure Standards for Airborne Contaminants annually. The WES document specifies, for each listed substance, the time-weighted average (TWA) concentration that the average worker may be exposed to for 8 hours per day, 5 days per week without adverse health effects, the short-term exposure limit (STEL) for 15-minute peak exposures, and where applicable, a ceiling limit that must not be exceeded at any time. The current WES document (2025 edition) includes over 700 substances. Where a WES is established for a substance used at the workplace, the risk assessment must evaluate whether worker exposures exceed or approach the WES and specify controls adequate to bring exposures below the WES.

**Nationally Significant Chemicals:** Some chemicals are subject to specific regulatory controls beyond the general WHS requirements. Asbestos is prohibited in most circumstances. Lead paint, mercury, certain organochlorine pesticides, and ozone-depleting substances are subject to specific management requirements. Where these substances are present at the workplace, the chemical risk assessment must reflect the specific regulatory controls applicable to each substance.

A chemical risk assessment must address both health hazards and physicochemical hazards. These two categories require different assessment methodologies and different controls.

**Health hazards** relate to the toxic, carcinogenic, mutagenic, reproductive, sensitising, or irritant properties of a chemical that can cause harm to the human body through acute or chronic exposure. Health hazard categories under GHS include: acute toxicity (Category 1–4, from fatal to harmful); skin corrosion and irritation; serious eye damage and eye irritation; respiratory sensitisation (causing occupational asthma); skin sensitisation (causing allergic contact dermatitis); germ cell mutagenicity (causing heritable genetic damage); carcinogenicity (Group 1A/1B known or presumed human carcinogens, Group 2 possible carcinogens); reproductive toxicity; specific target organ toxicity — single exposure (STOT-SE) and repeated exposure (STOT-RE); and aspiration hazard.

For health hazard assessment, the key questions are: What is the route of exposure (inhalation, skin contact, ingestion)? What is the likely concentration of exposure compared to the WES? How long and how often are workers exposed? Are any workers sensitised or otherwise at elevated risk?

**Physicochemical hazards** relate to the properties of a chemical that create hazards independent of their interaction with the human body — primarily fire, explosion, and reactivity hazards. Physicochemical hazard categories under GHS include: flammable liquids, gases, aerosols, and solids; explosive properties; oxidising liquids, solids, and gases; self-reactive and self-heating substances; substances that emit flammable gases on contact with water; organic peroxides; and substances corrosive to metals.

For physicochemical hazard assessment, the key questions are: What is the flash point and auto-ignition temperature of flammable liquids? What is the explosive limits range for flammable gases or vapours? Are there chemical incompatibilities between substances stored in proximity? Is there a risk of runaway exothermic reaction under abnormal process conditions?

A compliant chemical risk assessment follows the WHS risk management process, with steps specific to chemical hazards.

**Step 1 — Compile the chemical inventory.** List every hazardous chemical used, handled, generated, stored, or disposed of at the workplace. Obtain the current SDS for each chemical from the manufacturer or supplier. The SDS must be in the Australian format specified in the WHS Regulation (16-section format) and must be no more than 5 years old. Include intermediate chemicals generated in processes (e.g., welding fumes, combustion products, process by-products).

**Step 2 — Identify the health and physicochemical hazards.** For each chemical, extract the relevant hazard information from the SDS — the GHS hazard classifications, the WES (if listed), the routes of exposure, the health effects from acute and chronic exposure, and the physicochemical hazard properties.

**Step 3 — Assess exposure levels.** Estimate or measure the likely airborne concentration of each inhalation hazard using one or more of the following methods: qualitative assessment (using the control banding approach described in Safe Work Australia's Hazardous Chemicals Code of Practice); semi-quantitative modelling (using published emission factors for specific processes); or quantitative measurement (occupational hygiene air sampling in accordance with the applicable NIOSH or MDHS analytical method). Compare estimated or measured exposures against the WES. Assess the potential for significant skin or eye contact exposure for chemicals with dermal absorption or irritation hazards.

**Step 4 — Select controls.** Apply the hierarchy of controls: eliminate the chemical where a safer alternative exists; substitute with a less hazardous substance or formulation; implement engineering controls (local exhaust ventilation, enclosed processes, gloveboxes); implement administrative controls (work procedures, exposure time limits, health surveillance); and provide appropriate PPE (respiratory protective equipment, chemical resistant gloves, safety eyewear, and protective clothing) as a last resort and as a supplement to higher-order controls.

**Step 5 — Document, monitor, and review.** Record the assessment findings, implement the controls, monitor their effectiveness through air sampling or health surveillance where indicated, and review the assessment when the chemicals, processes, or workplace change.

The storage of hazardous chemicals introduces risks that are distinct from the risks of using or handling those chemicals, and a chemical risk assessment must address storage as well as use hazards.

The WHS Regulation specifies threshold quantities for different classes of dangerous goods above which specific storage controls are required. These thresholds are aligned with the Australian Standard AS 1940 (storage of flammable and combustible liquids), AS 3833 (storage of non-flammable, non-toxic gases), and the relevant state-based dangerous goods legislation.

Chemical segregation is critical to preventing reactive incidents and mixed-product fires. The following chemical incompatibilities are among the most common and most hazardous in workplaces:

- **Flammable liquids and oxidising agents:** Oxidising agents accelerate combustion and can ignite flammable liquids at ambient temperature. They must be stored separately. - **Acids and bases:** Mixing strong acids and bases generates heat and can cause violent reactions, splashing, and the release of toxic gases (e.g., mixing bleach with ammonia-based cleaners releases chloramine vapour). - **Water-reactive substances:** Substances such as alkali metals, acetic anhydride, and certain metal hydrides react violently with water. They must be protected from water ingress and stored away from water-based fire suppression systems. - **Oxidising agents and organic materials:** Many organic materials — solvents, oils, wood, paper — can be ignited by contact with strong oxidising agents such as nitric acid, hydrogen peroxide, or potassium permanganate.

The chemical risk assessment must include a segregation matrix identifying which chemicals may not be stored in proximity, the required separation distance or storage conditions, and the containment required to prevent mixing in the event of a spill or fire suppression.

For workers exposed to certain hazardous chemicals, health surveillance — periodic biological monitoring or medical examination to detect early signs of occupational disease — is required under the WHS Regulation.

The WHS Regulation specifies that health surveillance is required for exposure to chemicals for which there is a significant risk of a health effect occurring if the exposure is not adequately controlled, and for which there is a valid health surveillance method for detecting those effects. The chemicals for which health surveillance is specifically required under the WHS Regulation include: lead (blood lead monitoring), mercury (urine mercury monitoring), organophosphate pesticides (cholinesterase activity monitoring), and any substance listed in Schedule 14 of the WHS Regulation.

In addition to the specific requirements of the WHS Regulation, health surveillance is strongly recommended (and may be required by applicable codes of practice) for workers regularly exposed to Class 1A or 1B carcinogens, respiratory sensitisers (substances that cause occupational asthma), and substances with a low Threshold Limit Value (TLV) or WES that indicates significant toxicity at low concentrations.

A CIH-reviewed chemical risk assessment will identify where health surveillance is required or recommended, specify the appropriate biological monitoring method and monitoring frequency, and recommend the occupational physician or nurse who should conduct the surveillance.

Our complex consultant-drafted chemical risk assessments — which include a full chemical inventory, exposure assessment, health surveillance requirements, and a medical monitoring action plan — are priced at $65 AUD to reflect the greater depth of professional input required compared to a general workplace risk assessment.

Chemical risk assessment is one of the most technically demanding areas of WHS practice. The assessment requires knowledge of chemical toxicology, industrial hygiene measurement methods, exposure modelling, WES interpretation, GHS classification, and the hierarchy of chemical hazard controls — knowledge that most workplace supervisors and generic WHS consultants do not possess.

A Certified Industrial Hygienist (CIH) or Certified Occupational Hygienist (COH) has specialist training in recognising, evaluating, and controlling chemical workplace health hazards. The key contributions of a CIH to a chemical risk assessment include:

- Correct identification of the health endpoint of concern for each chemical (e.g., acute toxicity, carcinogenicity, sensitisation) and selection of the appropriate exposure limit and assessment method for that endpoint. - Accurate estimation or measurement of exposure levels using recognised industrial hygiene methods, including personal air sampling, area monitoring, and biological exposure monitoring. - Evaluation of control adequacy: whether the ventilation rate is sufficient to maintain exposures below the WES, whether the respirator selected has an adequate protection factor for the exposure level, and whether the PPE specification is consistent with the chemical resistance requirements. - Identification of chemicals that have no established WES but for which health effects are documented — and recommendation of precautionary exposure limits and controls based on the toxicological literature.

For complex chemical workplaces — industrial chemical manufacturing, chemical storage and distribution, pharmaceutical compounding, automotive refinishing, metal surface treatment, and food processing — a CIH-reviewed assessment is not merely preferable; it is the only way to ensure that the assessment captures the full scope of the chemical hazard and provides defensible evidence of due diligence if an occupational disease claim arises.

**What is a Safety Data Sheet and why is it important for a chemical risk assessment?** A Safety Data Sheet (SDS) is a document that the manufacturer or importer of a hazardous chemical must prepare in the GHS 16-section format, providing information about the chemical's identity, physical and chemical properties, health hazard classification, exposure limits, first aid measures, fire-fighting measures, accidental release measures, handling and storage requirements, exposure controls and PPE, and regulatory information. The SDS is the primary source of hazard information for a chemical risk assessment. The WHS Regulation requires PCBUs to obtain and keep a current SDS for each hazardous chemical at the workplace.

**What is the difference between a Workplace Exposure Standard and a safety threshold?** The Workplace Exposure Standard (WES) is the airborne concentration of a hazardous substance to which the average worker may be exposed, without experiencing adverse health effects, over a defined period (typically 8 hours per day, 40 hours per week). The WES is not a bright-line safety threshold — exposures below the WES do not guarantee safety for every worker, particularly for carcinogens (for which there is no safe threshold), respiratory sensitisers (for which sensitised individuals can react at any exposure level), and workers with pre-existing health conditions. The WES represents an acceptable exposure limit for the purposes of regulatory compliance, not an absolute guarantee of safety.

**How do I know if a chemical is a hazardous chemical?** A chemical is a hazardous chemical under Australian WHS law if it meets the criteria for classification as a hazardous chemical under the GHS. The SDS will identify the GHS hazard classifications for the chemical. Safe Work Australia's Hazardous Chemical Information System (HCIS) is a searchable database of hazardous chemicals and their classifications that can assist in confirming whether a substance is classified as hazardous.

**Is air sampling always required for a chemical risk assessment?** Not always. For chemicals with a low acute toxicity and a wide margin between the typical exposure level and the WES, a qualitative or semi-quantitative assessment may be sufficient. However, for chemicals with a WES in the range of parts per million (ppm) or milligrams per cubic metre (mg/m³), for carcinogens, for respiratory sensitisers, and for any situation where the exposure level is uncertain or variable, quantitative air sampling by a qualified industrial hygienist is required to provide an accurate exposure estimate.

**What records do I need to keep for a chemical risk assessment?** PCBUs must retain chemical risk assessment records, SDS files, and air monitoring results for the period specified in the WHS Regulation — generally five years for most records, but longer for health surveillance records (30 years) and records relating to asbestos or other carcinogens (40 years). Records must be accessible to workers, health and safety representatives, and regulatory inspectors on request.